Polymers comprising pyridyl groups have many applications, based on their basicity. When used in ion exchanging membranes or ion conducting membranes, these polymers must have a relatively rigid structure.
For example, it is known in the art to prepare crosslinked polymers comprising pyridyl groups by copolymerising polyvinylpyridine in the presence of divinyl monomers such as divinyl benzene. If more intricate shapes of the crosslinked polymers are desired, e.g. in films, shaping of the polymer must precede crosslinking. Very often linear poly(4-pyridine)s are then employed which are first formed into a film by e.g. casting and then crosslinked. In such a process, it is highly desirable that the crosslinking agent can mixed homogeneously into the polymer mass (melt or solution) to ensure a high homogeneity in the final product.
U.S. Pat. No. 3,770,666, incorporated by reference, discloses crosslinking of a copolymer of vinyl alcohol and 4-vinylpyridine via hydroxy groups by using chlorinated polyethylene oxide.
U.S. Pat. No. 4,474,869, incorporated by reference, discloses crosslinking of polyvinylpyridines by electron beam, ion beam or x-ray irradiation.
Hallensleben, Eur. Pol. J., 7, 1197-1203, 1971, incorporated by reference, discloses that the reaction of poly(4-vinylpyridine) with 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (chloranil) or 2,3-dichloro-5,6-dicyano-cyclohexadiene-2,5-diene-1,4-dione (DDQ) produces black, insoluble products, whereas the reaction of poly(4-vinylpyridine) with tetracyanoethene produces an electron-donor-acceptor complex that is soluble in polar, aprotic solvents such as DMF and DMSO. It is suggested that tetracyanoethene is capable of reversibly crosslinking poly(4-vinylpyridine).
L. E. Bromberg and M. G. Goldfield, J. Phys. Chem. B, 101, 966-970, 1997, incorporated by reference, disclose electron transfer reactions between poly(4-vinylpyridine)/divinyl benzene gels and various quinone derivatives which result into the formation of additional crosslinks within the gels. The quinone derivatives investigated were 2,3,5,6-tetrachlorocyclohexa-2,5-diene-1,4-dione (chloranil), 2,3-dichloro-5,6-dicyano-cyclo-hexadiene-2,5-diene-1,4-dione (DDQ) and 7,7,8,8-tetracyanoquinodimethane.
WO 2009/096786, incorporated by reference, discloses novel phenol compounds and (co)polymers comprising these novel phenol compounds.
Accordingly, there is a need in the art for a process for crosslinking polymer comprising 3-pyridyl and/or 4-pyridyl groups.